All known natural calcitonin peptides contain an amino acid sequence of 32 amino acids. Salmon calcitonin, for example, has the following formula: ##STR1##
In our U.S. Pat. Nos. 3,926,938, 4,062,815, 3,929,758 and 4,033,940 we disclose improved syntheses of calcitonins including the salmon calcitonin above referred to.
The natural calcitonins include the salmon calcitonins, bovine, porcine and ovine calcitonins and human calcitonins. All of these have serine at position number 2 except human calcitonin which has glycine at position number 2.